Conductor Size Research Articles

Analysis and Optimization of the Winding Loss of Flat-Wire Motors

The flat-wire motor has the characteristics of small size, low noise, high slot fill factor and good thermal conductivity in the slot. It can significantly improve the power density of the motor and is widely used in electric vehicles. The skin effect and proximity effect of the flat wire under high-speed conditions lead to high loss. Based on the established finite element model of a two-dimensional flat-wire motor, this paper first studies the high-frequency loss of different winding layers and the conductor sizes of each layer. Secondly, the influence of the magnetic field on AC loss is reduced by optimizing the tooth-tip height and tooth-tip width. Finally, it is verified that the high-frequency loss is reduced by 16% with the optimized layers, conductor sizes and tooth-tip sizes under the drive condition of the CLTC-P (China Light-duty Test Cycle—Passenger).

Microwave Photoconductivity of Gapless Dirac Fermions in HgTe Quantum Wells

The microwave photoconductivity of a system of gapless Dirac fermions in HgTe quantum wells with a critical thickness has been experimentally and theoretically investigated. It has been found that the photoconductivity fluctuates depending on the gate voltage near the Dirac point, and the fluctuation amplitude increases with an increase in the conductor size and a decrease in temperature. A theoretical explanation of the microwave response based on the assumption of the existence of a percolation two-dimensional fractal network of helical edge current states induced by fluctuations in the well thickness near the critical value has been proposed. It has been shown that the microwave photoconductivity of this network fluctuates with a change in the Fermi energy and the behavior of the fluctuation amplitude is in qualitative agreement with the corresponding experimental data.

Realisation of High-Frequency DRO Oscillators with Mosfet Transistors for Sub-MMWAVE Band

Abstract In high-frequency electronics, optimizing RF oscillators performance is essential, especially as applications reach into wide frequency bands. This article describes proposed clock generators for UWB sensor systems based on oscillators with dielectric resonator (DRO). Evaluation boards with different sizes of microstrip conductors were developed and tested, based on which new versions of boards were created. Improvements were made to integrate the DRO into a shielded box to ensure minimal external interference. The final designs demonstrated stable operation with low phase noise λ (1 MHz) = -108.805 dBc at fc = 21.732 GHz, sufficient power (3.65 dBm) and low power consumption(56 mW).

Deployment of Lifetime Cost Analysis to Reassess Economic Current Density in the Presence of Vietnam’s Market Economy

A decent choice of conductor size for overhead power transmission lines can provide economic advantages throughout the project’s lifetime. One of the crucial criteria for sizing conductors is economic current density. In Vietnam, the electricity industry has extensively utilized the 1950s-era economic current density that ignores the value of cash flow at diverse points in time and applies the assumption of the constant electricity tariff and wire cost. These costs, nonetheless, are likely to greatly impact the figures of economic current density; as a result, these figures must be modified. This paper puts forward novel figures of economic current density that are systematically determined on the basis of lifetime cost (LTC) analysis in the presence of Vietnam’s market economy. The LTC is made up of the initial capital expenditure (ICE) and the overall operating cost (OPC), which includes the expense incurred for maintenance and electricity energy loss. An analytical formulation of ICE related to conductor size and system voltage is established based on information from recently built overhead transmission lines and a regression-based method. The electricity energy loss is computed based on equivalent hours of maximum power loss contingent upon equivalent hours of maximum power usage throughout an analytical expression obtained on the basis of the regression technique from load consumption patterns in the past. Finally, the feasibility and efficacy of the proposed economic current density values are validated by practical case studies of overhead transmission lines in Vietnam. The deployment of the suggested strategy demonstrates a decrease in lifetime cost ranging from approximately 5% to around 20% in comparison to the methodology prescribed by the existing Vietnam standard.

Enhancing Electrical Distribution System Efficiency: A Software Tool Design for Conductor Cross-Section Optimization With TLBO Algorithm

In radial distribution networks with many separate branches and sections, it is very difficult to calculate the optimum conductor cross-section. This work introduces a new tool for optimizing conductor cross-sectional area in electrical distribution systems by utilizing the Teaching-Learning-Based Optimization (TLBO) algorithm. The tool can optimize the conductor crossection of the multisection, branching distribution systems. The maximum current carrying capacity constraint is taken into consideration when formulating the objective function to choose the ideal conductor size for each network segment. The optimal conductor sizes are determined by both desired percent voltage drop and current carrying capacity of the conductor. By calculating the currents drawn from the line segments in advance, the search space of the optimization algorithm is narrowed. MATLAB and Excel were used to determine the ideal conductor size. The conductor, which is chosen using the suggested method, will preserve appropriate voltage levels in radial distribution systems while optimizing the overall savings in conducting material and energy loss costs. The outcomes show that the optimal selection of conductor problem can be solved by the TLBO algorithm in a practical and effective manner. Results of testing the suggested tool on a radial distribution system are noteworthy.

Using Simplified Distflow-Based Mixed-Integer Quadratically Constrained Programming Formulation for Optimum Selection of Conductor Size in Electrical Distribution Networks

Determining conductor size is a subproblem that plays a vital role in the planning process of distribution systems. The problem of selecting the conductor cross-sectional area is usually made a model of mixed-integer non-linear programming (MINLP). It is important to note, however, that the MINLP model is not always capable of ensuring convergence to a solution that is globally optimum. In this research, a mixed-integer quadratically constrained programming (MIQCP) formulation is developed as a method for determining the conductor cross-sectional area in power distribution networks in an optimal manner. The goal function aims at minimizing the lifetime cost of lines, including initial capital cost together with operational expenses. The suggested optimization model’s constraints consist of power balance equations, thermal loading capacity of branches, nodal voltage restrictions, budget limitations for investment, and the need to have the same wire size in the main feeder. By using the simplified DistFlow approach for electrical distribution networks and precisely linearizing the product of a binary variable and a continuous variable, the MIQCP formulation is derived from the MINLP model. It is likely possible to solve the MIQCP formulation efficiently in the GAMS environment by using available commercial solvers like CPLEX. The developed MIQCP model is validated using three medium voltage distribution grids of IEEE 33 buses, IEEE 85 nodes, and the Vietnamese real 102 buses. The calculation results revealed the accuracy along with the efficacy of the proposed optimization procedure.

Near surface assessment of New capital city using geophysical techniques

ABSTRACT The Egyptian government announced the creation of a brand new capital city to address Cairo’s rapid population expansion and improve the quality of life for citizens, which is thought to have a strong demand for housing. In this study, we focused on the application of geophysical techniques, specifically Electrical Resistivity Tomography (ERT) and Very Low Frequency Electromagnetic Method (VLF-EM), to investigate the shallow subsurface in the New Capital city in Egypt. The study area is located in the eastern part of Cairo and is characterised by Oligocene and Miocene rocks. The ERT profiles reveal four geoelectrical layers based on resistivity values, with the first layer (Resistivity >300 Ω.m) interpreted as sand and conglomerate on the surface or basalt below. The second layer (100–300 Ω.m) is identified as sandstone, while the third layer (15–100 Ω.m) is interpreted as humid sandstone. The fourth layer (1–15 Ω.m) is characterised as shale. The abrupt changes in resistivity values horizontally indicate the probability of subsurface structures, including faults. The VLF-EM method is used to identify faults and cracks in the earth’s crust. The results provide information on the size, shape, and depth of both shallow and deep subterranean conductors. Anomalies of high conductivity suggest fault or fracture zones influencing underlying strata.

Neutral Currents in Large Public Lighting Networks

The modern large public lighting networks are characterized by two major aspects that rise problems from both power quality and neutral current point of view in low voltage wye-connected three-phase electrical systems: (i) the supply system is unbalanced loaded; (ii) the presence of discharge sources. It is important to underline that nowadays,these aspects are not taken into account in the proper sizing of neutral conductors. The paper presents a simplified but enough accurate methodology to estimate the RMS value of neutral currents in lighting networks. The theoretical relationships are illustrated for a three-phase public lighting network that contains high pressure sodium lamps.

Power factor correction of three-phase electrical power supply by using of thyristor controlled reactor VAR compensator

Low power factor (abbreviated as pf), particularly lagging pf, brings a lot of negative effects to electrical power supply system. Lagging pf is caused by inductive load. Inductive load with low pf draws higher current for the same active power demand. Higher current results in larger kVA rating and size of all electrical equipment connected to the electrical power system, larger conductor size used to deliver electrical power to the load, higher loss hence poorer power distribution efficiency and higher voltage drop hence poorer electrical power system voltage regulation. Considering all these negative effects, reactive power (VAR) compensation is needed. This paper analyses characteristics of a VAR compensation method called Thyristor Controlled Reactor (TCR) applied in three-phase electrical power system supplying an inductive load. A TCR consists of three sets of a capacitor connected in parallel with an inductor. The capacitor will supply a certain amount of reactive power needed by the load. The inductor is connected in series with an electronic static switch named as TRIAC to control the amount of reactive power absorbed by it. When reactive power supplied by the capacitor is higher than reactive power demanded by the load, the switching angle of TRIAC is controlled in such a way that excess of reactive power supply is absorbed by the inductor. In this work, three capacitors in which capacitance of each of it is equal to 50 µF as well as three inductors in which inductance of each of it is equal to 200 mH are used to compensate an inductive load which has power and pf vary from 1.5 kW to 4.6 kW and 0.46 to 0.84 respectively. By controlling the switching angle of TRIAC, pf of the three-phase electrical power system is successfully maintained close to unity at 0.95 following changes of the load. However, further analysis shows that operation of the TRIAC results in increase of current harmonics. Average of total current harmonic distortion (THD) increases from 15.13% to 18.45% due to use of TCR. On the contrary, voltage total harmonic distortion (THDV) after TCR installation is slightly lower than before TCR installation.

Electromagnetic-thermal co-optimization to minimize case-to-winding temperature rise in permanent magnet machines

Electrification of aerospace platforms requires efficient heat dissipation from electric machines to meet their temperature requirements while minimizing the weight and size of the onboard thermal management system. It is critical to couple available electromagnetic design optimization approaches with complementary thermal models, so that these thermal management system objectives can be considered, namely to reduce the temperature rise between the sources of heat generation and coolant. In this work, a thermal equivalent circuit model for the stator of a permanent magnet synchronous machine is developed and validated. The thermal network includes a discretization of individual conductors and considers their placement within a slot, compared to previous approaches that assumed a lumped/homogenized representation that is not versatile for robust optimization. The temperature predictions reveal that the choice of conductor sizing and packing within the stator slot significantly affects their peak temperatures. After validation, the thermal model is coupled to an electromagnetic model to perform multi-physics multi-objective design that minimizes machine mass and the temperature rise between the conductors and coolant. This approach contrasts a traditional electromagnetic design trade off between loss and mass. Design studies were performed to generate Pareto-optimal designs for comparison between these objectives. By using the co-optimization design framework with an integrated thermal objective function, the machine operating temperature can be significantly reduced while delivering the same power density at the cost of machine efficiency. The detailed machine designs are analyzed to explain the thermal advantages of the co-optimization design.

Analysis of Radial Distribution Systems by using Particle Swarm Optimization under Uncertain Conditions

Abstract: Losses in the network are one of the most important parts of a power distribution network, and work should be done to lower their value. The research used the Particle Swarm Optimisation (PSO) metaheuristic algorithm to investigate the impact of concurrently optimising phase balance and conductor size on the planning issues and objective functions of an imbalanced distribution system. These objective functions include power loss, voltage unbalance, total neutral current, and complicated power unbalance. Firstly, the optimisation process is applied to each goal function. Then, they are put together with weights to form a multi-objective optimisation problem. In this study, it was tried to find out how to minimise losses in electrical power distribution networks that aren't fair. Power flow and optimal DG placement are two PSO techniques that may be used to reduce losses. These changes may be applied to existing distribution systems using an effective load-flow method for a three-phase imbalanced radial distribution network. Knowing the node voltage, angle, branch current, actual power loss, wattles power loss, branch losses, etc. helps determine the network's true state. Simple formulae may be used to describe the relationship between the voltage at one end of the distribution system, the voltage at the other end, and the voltage drops throughout the whole system. An approach is developed to identify the relevant variables. The voltage's angle at the target is calculated with its magnitude. It's a process that requires time and effort. From the substation to each terminal node, the constant voltage of 1p.u. is considered. Voltage magnitude and phase angle are varied between repetitions, and voltage reductions are computed using the new parameters. The suggested approach has been applied to 19- and 25-node networks with unequal distribution. To demonstrate its efficacy, the recommended approach's speed requirements were compared to those of another recently developed technology. Good outcomes are achieved, and DG proves to be a viable option for reducing costs and improving performance.

The second moment of Dirichlet twists of a text {GL}_{4} automorphic L-function

In this paper, we give an asymptotic formula for the second moment of Dirichlet twists of an automorphic L-function L(s, pi ) on the critical line averaged over characters and conductors, where pi denotes an irreducible tempered cuspidal automorphic representation of {textrm{GL}}_{4}({mathbb {A}}_{mathbb {Q}}) with unitary central character. We give some hybrid bound for the error term with respect to the size of conductors of Dirichlet characters and that of the automorphic representation.

Sensitivity Analysis Based New Numerical Approach with Green Function for Optimization

In this study, sensitivity analysis based on a new numerical approach is developed for the three-dimensional structural optimization of high voltage system devices. It has been developed using Green’s theorem in a closed form to satisfy all boundary conditions and necessary conditions, including material and geometric dimensions. The developed sensitivity function and objective function are suitable for structural optimization of all electrostatic problems. The suitability and application of the developed function were made on the bushing. The changing geometry information was obtained from the developed sensitivity function as a result of the optimization. The analysis made with the classical design and the developed function were compared with each other. Optimization with the developed function has provided insulation and conductor size reduction. Experimental test devices before and after optimization process produced and tested. These results are presented in the study.

Moving towards a methodology for conductor sizing and protection in LVDC microgrids

Future power systems will be increasingly evaluated on their overall efficiency and sustainable use of raw materials. From this point of view, low-voltage DC networks have distinct advantages over AC networks. A large research interest is noted where these benefits are highlighted through case studies and demonstrators worldwide. However, the protection of DC networks is very challenging due to the absence of natural zero-crossings and fast network dynamics, and a general design methodology is missing in literature. This paper presents a general design methodology for the dimensioning of conductors and design of their protection in LVDC grids, in order to work towards a set of universal design methodologies for the development of LVDC grids based upon standards, best practices and experience, as is already a common resource in AC. The methodology is verified through a case study, where the differences with AC are highlighted and recommendations are made for standardization committees.

Shielding Effectiveness Measurement Method for Planar Nanomaterial Samples Based on CNT Materials up to 18 GHz

The study and measurement of the shielding effectiveness (SE) of planar materials is required to predict the suitability of a certain material to form an enclosed electromagnetic shield. One of the most widely used standards for measuring the SE of planar materials is ASMT D4935-18. It is based on a coaxial sample holder (CSH) that operates up to 1.5 GHz. Due to this standard’s frequency limitations, new variants with higher frequency limits have been developed by decreasing the size of the CSH conductors and the samples. However, this method and its high-frequency variants require two types of samples with very specific geometries and sizes. This method is unsuitable for certain types of nanomaterials due to their complex mechanization at such undersized scales. This contribution proposes an alternative SE measurement method based on an absorber box that mitigates the problems presented by the ASTM D4935-18 standard. The SE of rigid nanomaterial samples based on several concentrations of multi-walled carbon nanotubes (MWCNT) and two different fiber reinforcements have been obtained.

Magnetoneurography to investigate the mechanisms underlying the P9 far-field potential

ObjectiveThe mechanism underlying the generation of P9 far-field somatosensory evoked potentials (SEPs) is unresolved. Accordingly, we used magnetoneurography to visualize the current distribution in the body at the P9 peak latency and elucidate the origin of P9 generation. MethodsWe studied five healthy male volunteers without neurological abnormalities. We recorded far-field SEPs after median nerve stimulation at the wrist to identify the P9 peak latency. Using magnetoneurography, we recorded the evoked magnetic fields in the whole body under the same stimulus conditions as the SEP recording. We analyzed the reconstructed current distribution at the P9 peak latency. ResultsAt the P9 peak latency, we observed the reconstructed current distribution dividing the thorax into two parts, upper and lower. Anatomically, the depolarization site at the P9 peak latency was distal to the interclavicular space and at the level of the second intercostal space. ConclusionsBy visualizing the current distribution, we proved that P9 peak latency originates in the change in volume conductor size between the upper and lower thorax. SignificanceWe clarified that magnetoneurography analysis is affected by the current distribution due to the junction potential.

Thermodynamic optimization of 10–30 kA gas-cooled current leads with REBCO tapes for superconducting magnets at 20 K

Thermodynamic optimization is carried out to minimize the refrigeration work of gas-cooled current leads at a current level of 10–30 kA for superconducting magnets at 20 K. The binary HTS lead is a serial combination of REBCO (rare-earth barium copper oxide) tapes as cold part and copper conductor as warm part. In gas-cooled leads, liquid nitrogen is not used, but cold helium gas is supplied for forced-flow cooling through the channel between spiral fins of copper conductor. A special attention is paid to the conditions of gas-cooling, which can be integrated with a closed refrigeration cycle without any heat intercept or boil-off loss of liquid. The input power for refrigeration is rigorously calculated with the temperature-dependent properties of conductors. When a safety margin is selected on the critical current of REBCO, it is proven that there exists a unique optimum in the cooling-gas temperature and the dimensional size of copper conductor to minimize the required work for refrigeration. The results are compared with the optimized cases of conduction-cooled and vapor-cooled binary leads for 20 K magnets. The details of optimization procedure and design data are presented for practical application.

Application of the Gradient-Based Metaheuristic Optimizerto Solve the Optimal Conductor Selection Problemin Three-Phase Asymmetric Distribution Networks

This study addresses the problem of selecting the conductor sizes for medium-voltage distribution networks with radial configurations. The optimization model that represents this problem is part of the mixed-integer non-linear programming (MINLP) models, in which a power flow must be solved for each possible combination of conductor sizes. The main objective of this optimization problem is to find the best set of conductor sizes that minimize an economic objective function composed of the total costs of conducting materials added with the expected annual costs of the energy losses by proposing a new hybrid optimization methodology from the family of combinatorial optimization methods. To solve the MINLP model, a master–slave optimization method based on the modified version of the gradient-based metaheuristic optimizer (MGbMO) combined with the successive approximation power flow method for unbalanced distribution networks is presented. The MGbMO defines the set of conductor sizes assignable for each distribution line using an integer codification. The slave stage (three-phase power flow) quantifies the total power losses and their expected annual operating costs. Numerical results in the IEEE 8-, 27-, and 85-bus grids demonstrate the effectiveness of the proposed master–slave optimizer when compared with multiple combinatorial optimization methods (vortex search algorithm, the Newton-metaheuristic optimizer, the traditional and Chu and Beasley genetic algorithms, and the tabu search approaches). Two scenarios regarding the demand behavior were analyzed for the IEEE 8- and 27-bus grids: a peak load operation was considered, and, for the IEEE 85-bus grid, the daily demand behavior, including the presence of renewable generators, was considered. The 85-bus grid allowed showing that the most realistic operative scenario for selecting conductors is the case where a demand curve is implemented since reductions over 40% in the annual investment and operating costs were found when compared to the peak load operating condition. All numerical validations were performed in MATLAB software.

Application of Three-Phase Power Flow Analysis to the Nigerian Distribution Networks

Single-phase power flow analysis is used to study most distribution networks in Nigeria. The use of single-phase-power flow analysis assumes that the network is balanced and that the conductor phases act identically. However, Nigerian distribution networks are highly imbalanced because of untransposed lines, irregularly distributed loads in conductor phases, mismatched conductor sizes, and spacing. Consequently, single-phase modeling of the networks fails to reflect actual network behavior, resulting in an incorrect power flow solution. This research presents the three-phase modeling of radial distribution networks for a three-phase-power flow study of Nigerian distribution networks. Olusanya's 54-bus and Ajinde's 62-bus distribution networks in Nigeria were evaluated, both of which were very imbalanced. Without making any assumptions about the network components, these two distribution networks were properly modeled. Each network's three-phase power flow study was carried out in the MATLAB environment. The power flow solutions for each network demonstrated unevenness in the voltage profile for each network phase, as well as inequality in the real and reactive power losses in each phase, indicating that the deployed three-phase-power flow analysis properly mirrored the underlying network characteristics. Therefore, applying three-phase power flow analysis to distribution networks is critical for proper assessment of distribution network performance.

Minimizing the Active Power Losses and Retaining the Voltage Profile of the Distribution System Using Soft Computing Techniques with DG Source

The motivation of this research is to curtail the active power losses in the radial distribution system. This paper proposes a novel voltage stability indicator to determine the optimum conductor sizes for various distribution lines and find the conductor stability limit. This work proposes a new BAT algorithm for finding the optimal switching configurations using reconfiguration, which is used to minimize the active power losses. The proposed BAT algorithm gives the optimal locations to place the required amount of DG sources to improve the stability and minimize the power losses and maintain the voltage profile of the systems. The proposed BAT algorithm has been executed with the MATLAB 2016 software and compared with the differential evolution technique for IEEE 33 bus, IEEE 69 bus, and Indian real time 62 bus systems. The test results are applied on different conductors, and the real power flow on the different conductors are mapped in the proposed method using the novel voltage stability indicator. The radial distribution system has lower power losses, best voltage profile, cost of saving the DG source, optimal placing of a suitable rating of the DG source, optimal location of the DG source, and cost of saving the DG source which were achieved in this work. In this research, the distributed load flow analysis is implemented to find the parameters by the forward-backward sweep algorithm. The minimum bus voltage 0.95 pu is virtual in all the conductors. The loss reduction in the DE for IEEE 33 bus has been reduced from 42.4% to 45.3% and the loss reduction in IEEE 69 bus from 36.2% to 38.8% and the real time 62 bus from 47.5% to 49.15%. The loss reduction in the BAT algorithm for IEEE 33 bus has been reduced from 38.46% to 45.3% and the loss reduction in IEEE 69 bus is from 32.2% to 38.8%. The Indian standard real time 62 bus has been reduced from 38.92% to 49.15%. The proposed results are compared with the DE and BAT algorithm. The proposed BAT algorithm is found to be more effectual in reducing voltage deviation (VD) and reducing the power losses in the system.